The invention relates to a method for operating an inverter, particularly a pulse-controlled inverter, wherein the inverter has a plurality of phase systems, each with an outer conductor and at least one semiconductor component, and also a temperature monitoring device that has a plurality of temperature sensors, wherein the temperature sensors are used to sense the temperature of at least one portion of at least one of the phase systems. The invention also relates to an inverter.
Methods of the type cited in the outset are known from the prior art. They are used for operating the inverter. In this case, the inverter has the task of converting a direct current into an alternating current. The reverse direction may also be provided, that is to say conversion from alternating current to direct current. The inverter has a plurality of phase systems, wherein each phase system has an associated outer conductor. The outer conductors have the alternating current applied to them, and in this respect they are situated on an alternating current side of the inverter. Each phase system has the at least one semiconductor component associated with it. By way of example, in order to convert the direct current into alternating current, the semiconductor component can be used to periodically connect the outer conductor such that the alternating current is present on the outer conductor. The semiconductor components of the plurality of phase systems are usually controlled such that the alternating current applied to the outer conductor is present with a phase offset between the phase systems. However, further, non-switchable semiconductor components may also be provided. The inverter and the semiconductor components are actuated using an appropriate control circuit or a controller on which a control program is executed.
The semiconductor components have a characteristic nonreactive internal resistance that, when a current flowing through the respective semiconductor component is present, results in the introduction of heat into said semiconductor component and hence in a rise in temperature. When no current is flowing through the semiconductor component, on the other hand, it emits heat to its environment and matches its temperature to the temperature of the environment over the course of time.
In order to protect the inverter and particularly the semiconductor components from overheating, which involves the inverter or at least a region of the inverter exceeding an admissible maximum temperature, the inverter has the temperature monitoring device. This has a plurality of associated temperature sensors that can be used to sense or are used to sense the temperature of at least one portion or region of at least one of the phase systems. Preferably, each phase system has at least one of the temperature sensors associated with it. Owing to heat conduction effects and/or heat transfer effects, the temperature sensed by means of the respective temperature sensor usually corresponds not to the temperature of the overall phase system but rather to that of only a portion of said phase system. However, if the phase system has an associated element made of a material that is a good conductor of heat and that is in physical contact with regions of the phase system that are to be cooled, and if the temperature sensor is arranged on said element, then it can at least approximately be assumed that the sensed temperature substantially corresponds to the actual temperature of the phase system. By way of example, the element is a heat sink for the phase system or for the inverter and may be part of a cooling device thereof.
If a defect in or damage to at least one of the temperature sensors arises, said temperature sensor cannot be used, or at least can no longer be used, to reliably sense the temperature. For example, the case may arise in which the damaged or defective temperature sensor transmits a constant temperature to the temperature monitoring device. If this constant temperature is not above a maximum temperature that is the maximum admissible for the inverter, the temperature monitoring device permits further operation of the inverter or cannot deactivate the inverter in the event of the corresponding phase system overheating. Hence, the inverter or at least the respective phase system can sometimes be damaged by the overheating.